Meanwhile, along comes the urbane maverick Marcel Duchamp, who puts himself in opposition to this time- honoured status quo by presenting art as a matter of selection, the sexual act as a dysfunctional machine and himself, the artist, in bad-drag alter ego as Rrose Selavy. Fuelled by Freud, fanned by Surrealism, the gender genie is now out of the bottle, and sex becomes the Big Theme of 20th- century art, to be depicted, dissected and transgressed - the key to our identity and the curse of our existence. By the time we arrive at the Aids-poisoned playground of the 1990s, no sexual stone has been left artistically unturned, traditional divisions and categories no longer apply, and difference has become dynamic rather than divisive.
This, at least, is the thesis laid out in "Feminin-Masculin: Le sexe de l'art", the Pompidou Centre's mammoth artistic sexathon which reverses Jean-Luc Godard's 1965 movie title to put the girls on top and to negotiate the sex-steeped art of the 20th century. In keeping with the show's claim that modern artists have challenged conventions of sex and gender, old- style considerations of chronology or artistic category are jettisoned in favour of five sections (or "sexions", as the organisers embarrassingly call them) which chart an appropriately fluid, ambiguous course through the 500 or so exhibits, grouping them together according to similar or sympathetic preoccupations.
This results in some strange alliances. In the "Origin of the World" genital zone, for example, Claes Oldenburg's fabric light plug wilts before Anish Kapoor's stony void; Duchamp as the fictional Rrose along with his moustachioed Mona Lisa preside over a riot of "Identities and Masquerades"; and over in "Natural Histories" Georgia O'Keeffe is joined by Gilbert & George. Meanwhile, in the section devoted to "Attractions and Repulsions" the comings and goings span Duchamp, Francis Picabia and Rebecca Horn's sex machines through to Picasso's savage couplings and Bruce Nauman's video of escalating domestic violence; while amid the peeping and prying in "Stories of the Eye", power structures are scrambled when the elegant paedophile fantasies of Hans Belmer are confronted by the psychodrama of Eric Fischl's incestuous painting Birthday Boy.
However, Georges Bataille was right when he said that "eroticism always entails a breaking-down of established patterns", and the most powerful pieces in this show leap out of even these flexi-categories to transcend gender and agenda. The elegantly impotent mechanistic couplings in Marcel Duchamp's Bride stripped by her bachelors, or Helen Chadwick's knobbly bronze Piss Flowers, with their stamens made from casting female piss holes in the snow, would be at home in any part of "Feminin-Masculin", as would Louise Bourgeois's sleek, squatting, multi-breasted wolverine Nature study, which taps into a universal and androgynous eroticism that claims no specific artistic constituency.
Things have certainly moved on since the last full-scale attempt to take stock of the relations between art and sex. EROS, the "exposition intERnatiOnale du Surrealisme", held in Paris at the Daniel Cordier Gallery in 1959-60, was an attempt to investigate the theme of Eros (love), described by the exhibition organisers Andre Breton and Marcel Duchamp as "mankind's greatest mystery". In the same way that the Surrealist round-table "Inquiries on Sexuality" some 30 years before had almost completely excluded women, so in EROS women were relegated to muse status, from the cavorting painted nuns of Clovis Trouille, to the room with a trembling pink-satin ceiling and "vaginal door" leading to a corridor filled with moans and ending in a red chamber containing a cannibalistic feast.
"Feminin-Masculin" puts the record straight by representing Surrealist art in a context that accords equal status to other desires and sensibilities. The result is a re-invigoration of some of this century's most familiar icons - although the absence of a major Salvador Dali is a glaring omission. Now Magritte's bare-faced Le Viol and Meret Oppenheim's fur teacup and saucer can share a transgressively hairy moment with Jana Sterbak's chest- wig nightgown and Robert Gober's hermaphrodite wax pillow-torso; and Man Ray's phallic image of Lee Miller's neck can sit beside Annette Messager's photograph of a hefty penis which, with a few judicious strokes of a marker pen, has been transformed into a perky pussycat.
Not only in the title of this show is the feminine reasserted. Nancy Spero has painted goddesses, angels and heroines directly on to the perspex membrane of the Pompidou's escalators so that the panorama of Paris, the city viewed by the Surrealists as an outstretched female body complete with erogenous zones, now falls away beneath the soaring images of Josephine Baker, Isis et al.
Back on the gallery floor, Allen Jones's S&M slavette (who, in true art- historical tradition acts as a base for a palette-shaped table) is given rightful status as a piece of knowing, pneumatic kitsch by her proximity to Sylvie Fleury's First Spaceship on Venus, where vast, thrusting toy rockets poke through a wall of vivid green fun-fur.
Taking over from Surrealism's Sadean fantasies, Abstract Expressionism's angst and Pop's pin-ups, women appear to be upping the sexual ante. There is the brazen obscenity of Cindy Sherman's hermaphrodite dummy, consisting of two conjoined trunks ending in livid genitals topped off with cock ring and tampon string, or Sue Williams's savage monument to battered women where a prone, bruised figure is covered in crudely painted cliches explaining her swollen eye and kick marks. Three new wall-pieces by Cathy de Monchaux are lethal extravaganzas of spiky metal ornament and fleshy folded leather, sprung like traps and clogged with poisonous-looking powder, which bristle with association and innuendo and take up beauty as a bait and a defence.
In this ambiguous realm of pain and pleasure, if one figure emerges as the presiding genius over the new order conjured up by "Feminin-Masculin", it is not Marcel Duchamp or Pablo Picasso but the 84-year-old French-American Louise Bourgeois. The exhibition opens with her massive Twosome, in which giant black steel cylinders laboriously dock and separate, shunting along rails to the accompaniment of flashing red lights; and throughout the exhibition instinct and intellect are made to combine in the almost overwhelming physical presence of her works, ranging from the hand-sized bronze Janus Fleuri, which dangles ominously overhead like a hermaphrodite boomerang, a wall-relief of pink latex breasts-cum-polyps, or the room-within-a-room cylindrical lair containing racks of alchemical glass containers devoted to Precious Liquids.
"Feminin-Masculin" is a massive, overambitious orgy of an exhibition which still has some glaring omissions. Surely no survey of sex and art could ignore the unholy alliance between Jeff Koons and La Cicciolina? But it stands as a crucial challenge to both artistic and sexual stereotyping. It avoids moral judgements and deliberately (some may say, excessively) focuses on work that is explicit and transgressive. It could therefore never be seen in this country. Even the current Turner Prize exhibition at the Tate Gallery in London carries a warning sign that some exhibits (Damien Hirst's Mother and Child Divided? Mark Wallinger's Royal Ascot videos of the Queen and Duke of Edinburgh?) may be unsuitable for children.
At "Feminin-Masculin" there was no such anxiety among the parents and children wandering round the show. When asked if she expected any trouble from the press or the public, the Pompidou's press officer looked blank: "But this is an art show." If only we could be as mature about sex in art on this side of the Channel.
n 'Feminin-Masculin' is at the Centre Georges Pompidou, Paris to 12 Feb 1996 (00 331 447 81233)